1. Field of the Invention
The present invention relates to use of orthogonal spectrum bands in cellular networks, and particularly to a spectrum-efficient secondary users grouping method for two-tier cognitive radio networks.
2. Description of the Related Art
The trend in wireless communications industry has been always towards enhancing spectrum efficiency and energy efficiency of system operation. The drive for enhancing energy efficiency is mainly to satisfy the requirements of “green communications” and to extend the battery lifetime of user equipment (UE). On the other hand, the need to promote spectrum efficiency of future communications systems was raised in order to overcome the spectrum scarcity problem, and at the same time, to allow for increasing data rate transmission to satisfy the needs of emerging applications and services
Cognitive radio (CR) is a self-organized radio that can sense the spectrum, select the suitable channel to use, transfer from a spectrum band to another band when necessary, and share the spectrum with other radios. Cognitive radio was originally proposed to allow unlicensed secondary users (SUs) to utilize the spectrum allocated to primary users (PUs) when it is idle. Spectrum trading, defined as the process of selling and buying spectrum between the PUs and the SUs, is employed by CR networks to serve their SUs. One of the major issues in spectrum trading is pricing, which involves determining the value of the spectrum to the buyer. Since achieving low spectrum price is crucial to the success of the SU network, there is a need for a mechanism that helps the SU network to reduce the amount of spectrum to be purchased from the PU networks.
Thus, a spectrum-efficient secondary users grouping method for two-tier cognitive radio networks solving the aforementioned problems is desired.